Wildlife advocates have reached a tentative agreement with the U.S. government in a dispute over an endangered fish in the Yellowstone River along the Montana-North Dakota border.

The case centers on a proposed irrigation dam and fish bypass northeast of Glendive, Montana. Federal officials say it would allow pallid sturgeon to reach upstream spawning grounds that they've been unable to access for decades.

A federal judge blocked construction of the $59 million project in September. That came after Defenders of Wildlife and the Natural Resources Defense Council said there was no proof the fish bypass would work.

Attorneys for the two sides said in a court filing that they plan to finalize by Dec. 30 an agreement that would allow the case to move forward.

Terms were not disclosed.